Memory device architecture

ABSTRACT

Row electrode drivers and column electrode drivers for a memory device are distributed within a footprint share by a memory cell array.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is being concurrently filed with U.S. patentapplication Ser. No. ______, titled “METALLIZATION SCHEME FOR INTEGRATEDCIRCUIT” filed on ______, 2012, by Everardo Flores et al. (attorneydocket no. MICRON.582A); U.S. patent application Ser. No. ______, titled“INTERCONNECTION FOR MEMORY ELECTRODES,” filed on ______, 2012, byHernan Castro et al. (attorney docket no. MICRON.584A); each of which isassigned to the assignee of currently claimed subject matter andincorporated by reference in its entirety.

TECHNICAL FIELD

Embodiments of the present invention generally relate to integratedcircuits and more specifically to architecture embodiments ofcross-point memory devices.

BACKGROUND

There are many different types of memory, including random-access memory(RAM), read only memory (ROM), dynamic random access memory (DRAM),synchronous dynamic random access memory (SDRAM), resistive memory, andflash memory, among others. Types of resistive memory include phasechange memory, programmable conductor memory, and resistive randomaccess memory (RRAM), among others. Memory devices are utilized asnon-volatile memory for a wide range of electronic applications in needof high memory densities, high reliability, and data retention withoutpower. Non-volatile memory may be used in, for example, personalcomputers, portable memory sticks, solid state drives (SSDs), digitalcameras, cellular telephones, portable music players such as MP3players, movie players, and other electronic devices. Various resistivememory devices can include arrays of cells organized in a cross pointarchitecture. In such architectures, the memory cells can include a cellstack comprising a storage element, e.g., a phase change element, inseries with a select device, e.g., a switching element such as an ovonicthreshold switch (OTS) or diode, between a pair of conductive lines,e.g., between an access line and a data/sense line. The memory cells arelocated at the intersections of two conductive lines, such as a wordline and a bit line, and can be “selected” via application ofappropriate voltages thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

Claimed subject matter is particularly pointed out and distinctlyclaimed in the concluding portion of the specification. However, both asto organization and/or method of operation, together with objects,features, and/or advantages thereof, it may best be understood byreference to the following detailed description if read with theaccompanying drawings in which:

FIG. 1 is an illustration depicting a perspective view of a portion of amemory array, according to an embodiment.

FIG. 2A is an illustration depicting a simplified plan view of a memoryarray architecture.

FIG. 2B is an illustration depicting general socket regions forconnecting word and bit lines to their drivers at edges of an activememory array.

FIG. 3A is an illustration depicting an alternative memory architectureof an active memory array partitioned into multiple sub-arrays,according to an embodiment.

FIG. 3B is an illustration depicting example socket interconnect regionsfor connecting word lines and bit lines of FIG. 3A to their drivers.

FIG. 4A is an illustration depicting an alternative memory architectureof an active memory array partitioned into multiple sub-arrays,according to an embodiment.

FIG. 4B is an illustration depicting socket interconnect regions forconnecting word lines and bit lines of FIG. 4A to their drivers.

FIG. 5 is an illustration depicting a plurality of interconnect levels,according to an embodiment.

FIG. 6 is an illustration depicting a top view of a portion of anexample implementation of a memory device comprising driver circuitrydistributed across a memory array footprint in a quilt pattern.

FIG. 7A is an isometric illustration depicting electrodes of a socketregion for forming vertical connector among and through multiple metallevels, including an interconnect level and two levels of word lines,according to an embodiment.

FIG. 7B is an illustration of a top view of one of the levels of wordlines and the vertical connectors of FIG. 7A.

FIG. 8A is a plan view of a pattern of sacrificial mandrels for use in apitch-multiplication process that can be used to create metal levelswith socket locations similar to that of FIG. 7B, according to anembodiment.

FIG. 8B is a plan view of a pattern of spacers that can be formed onsidewalls of the sacrificial mandrels of FIG. 8A to form conductivelines and vertical connectors by pitch-multiplication, according to anembodiment.

FIG. 9A is an illustration depicting multiple levels of a memory device,including three word line layers alternated with two bit line layers ina memory array, according to an embodiment.

FIG. 9B is an illustration depicting multiple levels of a memory device,including two word line layers sandwiching a bit line layer in a memoryarray, according to an embodiment.

FIG. 9C is an illustration depicting multiple levels of a memory device,including two word line layers sandwiching a bit line layer in a memoryarray, according to an embodiment.

FIG. 10 is an illustration of a torus to represent a relationshipbetween memory cell locations and electrode that address them for anarrangement of distributed drivers and staggered electrode lines,according to an embodiment.

Reference is made in the following detailed description to theaccompanying drawings, which form a part hereof, wherein like numeralsmay designate like parts throughout to indicate corresponding oranalogous elements. It will be appreciated that for simplicity and/orclarity of illustration, elements illustrated in the figures have notnecessarily been drawn to scale. For example, the dimensions of some ofthe elements may be exaggerated relative to other elements for clarity.Further, it is to be understood that other embodiments may be utilized.Furthermore, structural and/or logical changes may be made withoutdeparting from the scope of claimed subject matter. It should also benoted that directions and/or references, for example, up, down, top,bottom, and so on, may be used to facilitate discussion of drawings andare not intended to restrict application of claimed subject matter.Therefore, the following detailed description is not to be taken tolimit the scope of claimed subject matter and/or equivalents.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth to provide a thorough understanding of claimed subject matter.However, it will be understood by those skilled in the art that claimedsubject matter may be practiced without these specific details. In otherinstances, methods, apparatuses and/or systems that would be known byone of ordinary skill have not been described in detail so as not toobscure claimed subject matter.

Integrated circuits, such as integrated circuit memory devices, includemultiple layers of material typically built on a substrate. The materiallayers include conductive metal layers, also known as metal levels,which interconnect circuit devices. Elongate conductive lines of metallevels in an integrated circuit include interconnects as well aselectrode that function as electrodes for semiconductor devices (e.g.,word lines and bit lines for addressing memory cells, which can includeswitches and/or memory storage elements). Conductive lines formed from alayer or layers at the same vertical level can be referred tocollectively as a metal level, and the lines can be referred to metallines or wires, even though the material may be formed from non-metalconductors such as doped semiconductor layers (e.g., polysilicon) ormetallic alloys such as metal nitrides, metal carbides and metalsilicides. Contacts formed between metal levels can be referred to asvertical connectors. Such vertical connectors can be formed separatelyfrom the conductive lines they connect, or can be simultaneously formedwith overlying conductive lines in a dual damascene process.

References herein to memory “bit lines” are more generally applicable todigit lines that are not limited to binary memory storage. Furthermore,bit lines can be referred to even more generally as column electrodes,and references to bit line drivers and driver regions herein are moregenerally applicable to column drivers and driver regions. Similarly,word lines can be referred to as row electrodes, and references hereinto word line drivers and driver regions are more generally applicable torow drivers and driver regions. The skilled artisan will appreciate thatrow column electrodes need not be perpendicular; rather, an array can beconfigured in a manner in which the row and column electrodes cross oneanother at non-perpendicular angles.

In embodiments described herein, row and column driver regions (or wordline and digit line driver regions) are described as including rowdriver circuits and column driver circuits. In addition to drivercircuitry, the circuit level described below can include distributed orcontiguous additional circuitry for operation of the memory array withinthe shared footprint with a memory array, such as global drivers,repeaters, write circuits, sense amplifiers, word decoders, digitdecoders, etc. Collectively these circuits can be referred to as logiccircuitry for the memory array. For example, digit line drivers, sensecircuitry and digit decoders can be formed within column driver regions;word line drivers, word decoders, write circuits, global drivers andrepeaters can be formed within column drivers. The skilled artisan willappreciate that different types of logic circuits can be distributeddifferently among the row and column driver regions described herein,and that in some embodiments the additional circuitry can be within thefootprint of the memory array but outside the driver regions. Some typesof logic circuitry can remain outside the footprint of the memory array.

As explained above, a memory device may include memory cells arranged inan array format. A memory array generally may include two conductive, orsemi-conductive, crossing (e.g., orthogonal) lines referred to as a wordline and a digit line (e.g., bit line) that are used to access, programand read a memory cell. The word lines and bit lines can also serve aselectrodes for the memory cells and so can be referred to as electrodelines, or more simply as electrodes. Although different types of memorycells may be accessed, read and programmed in different manners, wordlines and bit lines are typically coupled to respective word line andbit line driver circuitry, also known and row and column drivers. Asused herein, the term “substrate” may include silicon-on-insulator (SOI)or silicon-on-sapphire (SOS) technology, doped and undopedsemiconductors, epitaxial layers of silicon supported by a basesemiconductor foundation, complementary metal oxide semiconductors(CMOS), e.g., a CMOS front end with a metal back end, and/or othersemiconductor structures and technologies. Various circuitry, such asdecode circuitry, for example, associated with operating memory arraymay be formed in and/or on the substrate. Furthermore, when reference ismade to a “substrate” in the following description, previous processsteps may have been utilized to form regions or junctions in the basesemiconductor structure or foundation.

FIG. 1 illustrates a perspective view of a portion of a memory array100. In this example, array 100 may comprise a cross-point arrayincluding memory cells 106 positioned at intersections of a first set ofconductive lines 102-0, 102-1, . . . , 102-N, e.g., access lines, whichmay be referred to herein as word lines, and a second set of conductivelines 104-0, 104-1, . . . , 104-M, e.g., data lines, which may bereferred to herein as bit lines. Coordinate axis 101 indicates that thebit lines 104-0, 104-1, . . . , 104-M are oriented in an y-direction andthe word lines 102-0, 102-1, . . . , 102-N are oriented in ax-direction, in this example. As illustrated, the word lines 102-0,102-1, . . . , 102-N are substantially parallel to each other and aresubstantially orthogonal to the bit lines 104-0, 104-1, . . . , 104-M,which are substantially parallel to each other; however, embodiments arenot so limited, and word lines and bit lines can have non-perpendicularorientations. As used herein, the term “substantially” intends that themodified characteristic needs not be absolute, but is close enough so asto achieve the advantages of the characteristic. For example,“substantially parallel” is not limited to absolute parallelism, and mayinclude orientations that are at least closer to a parallel orientationthan a perpendicular orientation. Similarly, “substantially orthogonal”is may include orientations that are closer to a perpendicularorientation than a parallel orientation.

Cross-point array 100 may comprise an array structure. As an example,memory cells 106 may comprise phase change random access memory (PCRAM)cells, resistive random access memory (RRAM) cells, conductive bridgerandom access memory (CBRAM) cells, and/or spin transfer torque randomaccess memory (STT-RAM) cells, among other types of memory cells. Invarious embodiments, memory cells 106 may comprise a “stack” structurethat includes a select device, e.g., a switching device, coupled inseries to a storage element, e.g., a resistive storage elementcomprising a phase change material or metal oxide. As an example, theselect device may comprise a diode, a field effect transistor (FET), abipolar junction transistor (BJT), or an ovonic threshold switch (OTS),among other switching elements.

In a number of embodiments, a select device and storage elementassociated with a respective memory cell 106 may comprise series coupledtwo-terminal devices. For instance, a select device may comprise atwo-terminal Ovonic Threshold Switch (OTS), e.g., a chalcogenide alloyformed between a pair of electrodes, and the storage element maycomprise a two-terminal phase change storage element, e.g., a phasechange material (PCM) formed between a pair of electrodes. Memory cells106 including a select device such as an OTS in series with a PCM can bereferred to as phase change material and switch (PCMS) memory cells. Ina number of embodiments, an electrode may be shared between a selectdevice and a storage element of a memory cell 106. Also, in a number ofembodiments, the bit lines 104-0, 104-1, . . . , 104-M and the wordlines 102-0, 102-1, . . . , 102-N may serve as top and bottom electrodescorresponding to the memory cells 106.

As used herein, “storage element” may refer to a programmable portion ofa memory cell 106, e.g., the portion programmable to different datastates. For example, in PCRAM and RRAM cells, a storage element mayinclude a portion of a memory cell having a resistance that isprogrammable to particular levels corresponding to particular datastates responsive to applied programming signals, e.g., voltage and/orcurrent pulses, for instance. A storage element may include, forexample, one or more resistance variable materials, such as a phasechange material. As an example, a phase change material may comprise achalcogenide alloy such as an indium(In)-antimony(Sb)-tellurium(Te)(IST) material, e.g., In₂Sb₂Te₅, In₁Sb₂Te₄, In₁Sb₄Te₇, etc., or agermanium(Ge)-antimony(Sb)-tellurium(Te) (GST) material, e.g.,Ge₈Sb₅Te₈, Ge₂Sb₂Te₅, Ge₁Sb₂Te₄, Ge₁Sb₄Te₇, Ge₄Sb₄Te₇, etc., among otherphase change materials. The hyphenated chemical composition notation, asused herein, indicates the elements included in a particular mixture orcompound, and is intended to represent all stoichiometries involving theindicated elements. Other phase change materials can include Ge—Te,In—Se, Sb—Te, Ga—Sb, In—Sb, As—Te, Al—Te, Ge—Sb—Te, Te—Ge—As, In—Sb—Te,Te—Sn—Se, Ge—Se—Ga, Bi—Se—Sb, Ga—Se—Te, Sn—Sb—Te, In—Sb—Ge, Te—Ge—Sb—S,Te—Ge—Sn—O, Te—Ge—Sn—Au, Pd—Te—Ge—Sn, In—Se—Ti—Co, Ge—Sb—Te—Pd,Ge—Sb—Te—Co, Sb—Te—Bi—Se, Ag—In—Sb—Te, Ge—Sb—Se—Te, Ge—Sn—Sb—Te,Ge—Te—Sn—Ni, Ge—Te—Sn—Pd, and Ge—Te—Sn—Pt, for example. Other examplesof resistance variable materials may include transition metal oxidematerials and/or alloys including two or more metals, e.g., transitionmetals, alkaline earth metals, and/or rare earth metals. Embodiments arenot limited to a particular resistive variable material or materialsassociated with the storage elements of the memory cells 106. Forinstance, other examples of resistive variable materials that may beused to form storage elements include binary metal oxide materials,colossal magneto-resistive materials, and/or various polymer-basedresistive variable materials, among others. Although not illustrated inFIG. 1, in a number of embodiments, array 100 may be implemented as partof a three dimensional (3D) architecture, with a number of arrays 100vertically stacked on each other, for example.

FIG. 2A is a simplified plan view of a memory array architecture 200where word line drivers 204 are located substantially within a footprintof an active array 202, i.e., under memory cells, and near a peripheryof the array. The active array 202 is outlined in FIG. 2A by the dashedoutline. Bit line drivers 206, conversely, are located generally outsideof the footprint of the active array 202. Inactive, dummy or fillerarrays 208 (FIG. 2B) may be located outside the active array and may beplaced over the bit line driver circuitry in a manufactured device. Eachset of drivers 204 or 206 is located near the edge of the array 202 intwo contiguous blocks of circuitry on opposite sides of the array 202.Those skilled in the art will appreciate that circuit details of thearray and driver circuitry is not provided in order to focus thedescription on the general layout of the architecture.

Word line and bit line driver circuits may be electrically coupled toword line 210 and bit line 212 conductors, respectively. Because thedriver circuits are positioned alongside the array periphery, thedrivers may be coupled through interconnect regions 214 and 216, whichcan be referred to as socket regions, to ends of the word lines and bitlines. FIG. 2B illustrates the general socket regions 214 and 216 forword and bit lines at the edges of an active array. This architecturemay be simple in design but less efficient in overall die size, lessefficient in the number or lithographic requirements of theinterconnects employed and less efficient in terms of driver circuitryrequirements as compared to the embodiments of FIGS. 3A-10, as describedand explained further below.

FIG. 3A illustrates an alternative memory architecture 300 including anactive memory array 302 partitioned into multiple sub-arrays, inaccordance with an embodiment. The sub-arrays are repeated in a regularfashion and so are also referred to herein as “tiles.” FIG. 3A is anexample of an architecture in which electrode drivers are distributedacross a footprint of an active memory array. In this example, there arefour sub-arrays 304, 306, 308 and 310 corresponding to one array 202 ofFIG. 2A. Word line drivers 314 may be located substantially within afootprint of the active array, under the memory cells, and near theperiphery of the sub-arrays. Bit line drivers 312 may also be locatedsubstantially within the footprint of the active array, under the memorycells, and near the periphery of the sub-arrays. It will be understoodthat each shaded area comprises a driver region that can includemultiple driver circuits, and so can represent a group of drivers. Inthe illustrated embodiment, individual sub-array layouts in a plan vieware identical to neighboring sub-arrays. That is, in this embodiment,the word line drivers 314 are in the upper left and lower right cornersof the sub-arrays, and extend generally along the y-oriented edges toconnect with word lines 330 that extend in the x-direction. The rowdriver regions, represented by the word line drivers 314 in FIG. 3A, areelongated in the column or y-direction.

Word line drivers 314 may be coupled to central locations along the wordlines 330, which may cross boundaries between adjacent sub-arrays, andmay also cross boundaries of other driver regions. As indicated by a dotalong each word line 330, the connection point, also known as a socket,between the word line 330 and its driver is positioned centrally alongthe word line, rather than at an end of the word line. In someimplementations, the connection point (socket) is closer to a mid-pointalong the word line 330 than to either end point of the word line 330.In some implementations, the connection point (socket) is positioned adistance of at least about 40% of the length of the word line 330 fromeither end of the word line 330, such that the connection point iswithin the middle 20% of the length of the line. The word lines 330 canhave generally the same length as the word lines of FIG. 2A. That is,the total number of bits coupled to a physical word line may be the samefor internally (FIG. 3A) or peripherally (FIG. 2A) connected word lines,although the distance to the terminal point of the word line from thedriver interconnect is reduced. For example, each word line 330 canserve about 1000-4000 bits for current technology nodes.

The bit line drivers 312 are in the upper right and lower left cornersof the sub-arrays of FIG. 3A, and extend generally along the edges alongthe x-direction to connect with bit lines 320 that extend in they-direction. The column driver regions, represented by the bit linedrivers 312 in FIG. 3A, are elongated in the row or x-direction. Similarto the word line drivers, the bit line drivers 312 may be coupled to acentral location of the bit lines 320, which cross boundaries betweenadjacent sub-arrays. As indicated by a dot along each bit line 320, theconnection point between the bit line 320 and its driver is positionedcentrally along the bit line, rather than at an end of the bit line. Insome implementations, the connection point is closer to a mid-pointalong the bit line 320 than to either end point of the bit line 320. Insome implementations, the connection point (socket) is positioned adistance of at least 40% of the length of the bit line 320 from eitherend of the bit line 320, such that the connection point is within themiddle 20% of the length of the line. The bit lines 320 can havegenerally the same length (number of bits) as the bit lines 212 of FIG.2A. It will be appreciated by those skilled in the art that the drivercircuits can be reversed, for example the word line drivers can be inthe lower left and upper right corners of the sub-arrays. In FIG. 3Aeach of the sub-arrays has the same layout.

In FIG. 3A, word lines 330 are shown as staggered, i.e., adjacent wordslines 330 are shifted with respect to one another along their axis ofelongation (x-axis). It will be understood from the further descriptionbelow that a group of word lines 330 can be co-extensive with oneanother and staggered with respect to adjacent groups of words lines 330(see, e.g., FIGS. 7B and 8B and attendant description). Similarly, bitlines 320 or groups of bit lines 320 are staggered in the architectureof FIG. 3A.

FIG. 3B illustrates socket interconnect regions 324 for the word linesand socket interconnect regions 322 for the bit lines of the arrayarchitecture of FIG. 3A. It is noted that the socket regions are at theboundaries of the sub-arrays. By breaking the word and bit line drivergroups and socket regions into smaller pieces and staggering the lines320 and 330, or groups of lines, in alternate rows, as illustrated inFIG. 3A, the bit lines 320 and word lines 330 can extend through theactive array 302 and through the socket regions 322 and 324.Accordingly, neither the socket regions nor the driver locations arerestricted to the array edges as in FIG. 2B.

FIG. 4A illustrates an alternative memory architecture 400 where theactive memory array 402 is partitioned into multiple sub-arrays. In thisexample, there are four sub-arrays 404, 406, 408 and 410 occupying thesame footprint as one sub-array 304 of FIG. 3A. Each of the smallersub-arrays 404-410 can be referred to as “patches” and together they candefine the larger repeating unit of a tile. FIG. 4A is another exampleof an architecture in which electrode drivers are distributed across afootprint of an active memory array. Like FIG. 3A, the row drivers,represented by word line drivers 412 in FIG. 4A are elongated in thecolumn or y-direction, while the column drivers, represented by bit linedrivers 414 in FIG. 4A, are elongated in the row or x-direction. Asignal path traversing a path in an x- or y-direction may alternatelypass over row and column driver regions.

Word line drivers 412 may be located substantially within the footprintof the active array and near the periphery of the sub-arrays. Bit linedrivers 414 may also be located substantially within the footprint ofthe active array and near the periphery of the sub-arrays. It will beunderstood that each shaded area comprises a driver region that caninclude multiple driver circuits, and so can represent a group ofdrivers. In the illustrated embodiment, individual sub-array layouts ina plan view may be mirror copies of layouts of adjacent sub-arrays. Thatis, in sub-array 404 the word line drivers 412 are in the upper left andlower right corners of the sub-array, and extend generally along theedges extending in the y-direction of the subs-array to connect withword lines 430 extending in the x-direction.

The word line drivers 412 may be coupled to a central location of theword lines 430, as explained for the socket location along word lines330 of FIG. 3A. Word lines 430 may cross boundaries between adjacentsub-arrays and may also cross boundaries of other driver regions. Thebit line drivers 414 are in the upper right and lower left corners ofsub-array 404, and extend generally along the edges extending in thex-direction of the sub-array to connect with bit lines 432 extending inthe y-direction.

It is noted that the bit line drivers 414 are coupled to a centrallocation of the bit lines 432, as explained for the socket locationsalong bit lines 320 of FIG. 3A. Bit lines 432 may cross boundariesbetween adjacent sub-arrays and may also cross boundaries of otherdriver regions. In adjacent sub-array 406 the word line drivers 412 arein the lower left and upper right corners of the sub-arrays, and extendgenerally along the edges extending in the y-direction to connect withword lines 430 extending in the x-direction. The bit line drivers 414are in the lower right and upper left corners of the sub-arrays, andextend generally along the x edges to connect with bit lines 432extending in the y-direction. Thus in a plan view the layout of thedrivers is a mirror image between adjacent sub-arrays 404 and 406.

As in FIG. 3A, both word lines 430, or groups of word lines, and bitlines 432, or groups of bit lines, are staggered in the architecture ofFIG. 4A. Unlike FIG. 3A there are now four levels of staggering for eachword line or group of word lines and each bit line or group of bit linesin the illustrated tile. The period represented by the group of fourword lines 430 can be repeated in tile adjacent in the y-direction, andthe period represented by the group of four bit lines 432 can berepeated in the tiles adjacent in the x-direction.

FIG. 4B illustrates the socket interconnect regions 420 for bit linesand socket interconnect regions 422 for word lines, of the arrayarchitecture of FIG. 4A. Only four of the sub-arrays of FIG. 4A areshown. It is noted that the socket regions are at the boundaries of thesub-arrays. By breaking the word and bit line driver regions and socketregions into smaller segments and staggering the lines or groups oflines in alternate rows, as illustrated in FIG. 4A, the word lines andbit lines can extend through the active array 402 and through the socketregions 420 and 422. Accordingly, neither the socket regions nor thedriver regions are restricted to the array edges as in FIG. 2B. Further,the pattern of the socket regions is different from FIG. 3B due to themirror pattern of the adjacent sub-arrays.

One skilled in the art will recognize that locating the word and bitline drivers is more than mere design choice. Location for the drivercircuitry affects performance of the memory and requires substantialarchitectural changes, as explained below, in the array andmetallization layers.

For the particular organization of array drivers and arrayinterconnection points (sockets) in FIG. 4A, substantial cost reductioncan be obtained in the driver (e.g., CMOS) circuitry to drive the arrayas well as the metal level connections from the driver circuitry to thearray of memory cells. FIG. 3A has an advantage of being able to fit alldrivers under the array, sharing the same footprint as memory cells in adensely packed manner, as compared to the arrangement of FIG. 2A. Theembodiment of FIG. 3A places all drivers under the array by breaking upthe driver groups into smaller pieces and locating the sockets in adistributed manner as compared to the FIG. 2A. This also enables thearray word lines and bit lines, which also serve as electrodes for thearray, to be driven from their midpoints. Driving the electrodes fromtheir midpoints confers advantages to the drivers due to reduction in IRdrop and RC delay as compared to the arrangement of FIG. 2A, because thefarthest cell along the line is about half the distance as for thefarthest cell in the arrangement of FIG. 2A, which can be of significantbenefit to certain types of cross-point memory cell technologies. Thisbenefit may be manifested in relaxed transistor requirements, circuitcomplexity, process complexity or circuit area for the driver circuits,as examples.

The architecture of FIG. 4A further dissects the driver groups andsocket regions into yet smaller pieces. It retains the advantages ofcentrally driven electrodes and uses a socket to support suchconnections. In addition, the architecture of FIG. 4A also centers thedriver groups (regions) with respect to their sockets, which can beunderstood by comparing the socket locations in FIG. 3A (dots along theelectrode lines are at the edges of the driver regions 312 and 314) withthe centered socket locations of FIG. 4A (dots along the electrode linesare in the middle of the driver regions 412 and 414. This has theadditional advantage of reducing the interconnection requirements fromdriver to socket. This reduced interconnection requirement may manifestitself as a relaxed pitch requirement on interconnect metal layers, or areduction in the number of interconnect metal layers, with a significantcost advantage, as compared with the less distributed arrangements ofFIG. 2A or FIG. 3A.

Yet another feature of the architecture of FIG. 4A is enabled by theplacement of the socket regions for crossing (e.g., orthogonal)conductors, in such a way that they never touch each other. Placing ofthe socket regions for orthogonal conductors in a disjointed patternallows the layout of the driver groups to be simplified, since in manymemory technologies the drivers of orthogonal electrodes are designed toemploy different transistor types or materials that should be keptseparate from each other. Another feature of the disjointed arrangementof socket regions for orthogonal conductors is that anytime a memorycell is accessed by the selection of a word line electrode and a bitline electrode, the worst case and best case distance of that particularcell from its socket is never the worst case or best case of any twoelectrodes. As an example, if a memory cell along a word line isfarthest away from its socket, its corresponding bit line locationcannot also be farthest away from its bit line socket. The same is trueof the memory cell along a word line that is closest to its word linesocket. This can be a significant performance advantage for memorytechnologies where that combined distance, which translates into alarger IR drop or longer RC delay, may impact the size of array or limitthe operating conditions of the memory device. This advantage mayalternatively be manifested by further relaxation of driverspecifications, such as circuit area, circuit complexity and processcomplexity as examples.

Although not illustrated, it will be apparent to one skilled in the artwith the benefit of the present disclosure that interconnecting with acentral point along the word line and bit line electrodes along with thedisjointed socket region organization can reduce the area required percircuit driver due to relaxed driver specifications by reduction indistance along the conductors from the socket to the farthest cell. Theindividual number of contiguous segments of socket interconnect regionsis larger as compared with a single ended socket implementation, andthus may have larger overhead, but this overhead is more thancompensated by being able to fit all drivers under the array and thereduced driver area required. The area under the active array madeavailable by the relaxed specification for the array drivers can be usedby other circuitry which can leverage the more efficient interconnectroutes enabled by the socket regions within the active array and withinthe driver groups.

An advantage of cross-point memory devices is the ability to “stack”multiple memory cells on top of each other. Because the memory cells arelocated at intersections of word and bit lines, by providing additionalword and/or bit lines the density of the memory array can be increased.Each layer of memory cells can be referred to as a deck. For a two deckmemory array a bit line layer can be sandwiched between two word linelayers. As such, in a two deck memory device the number of word linedrivers is doubled thereby increasing the die area occupied by word linedrivers.

With reference to FIG. 9A, which schematically shows metal levels of amulti-deck memory device. In one implementation, a four deck memoryarray has three word line layers alternated with two bit line layers.The memory includes word lines layers 902, 904 and 906, bit line layers908 and 910, a “glue” layer G1 912 and three layers of metal 914 (M1, M2and M3). All of the illustrated layers can be referred to as metallevels, including both interconnect layers 912-914 and electrode layers902-910.

For clarity of description, the glue layer 912 is provided with aseparate label from the other interconnect metal layers 914 of M1, M2and M3 and is treated as a separate class of interconnect herein. Thefunction of the glue layer 912 is to carry out the connections betweenthe array (represented by metal layers 902-910 in FIG. 9A) and the lowerlayers of the driver circuits (represented by metal layers 914 in FIG.9A). However, the glue layer can be a patterned metal layer, like theother metal layers. Moreover, the function of the glue layer mayalternatively be embedded in the lower layers by appropriatemodifications of these layers. Similarly the bit lines and word lines902-910 can be referred to as “electrodes” or “electrode lines” simplyto distinguish metal lines that form part of the memory array andfunction as electrodes therein from lower level interconnects 914 thatserve to connect semiconductor devices. Like the glue layer and othermetal layers of FIG. 9A, however, these lines can be patterned metallines. M1 can serve as a local interconnect and for strappingsemiconductor diffusion regions, whereas M2 and M3 can serve as longerdistance interconnects.

The top and bottom word lines 902 and 906 can be shorted together anddriven by a common driver circuit. As such, in a four deck memory devicethe number of word line drivers and bit line drivers are doubledrelative to a single deck memory device occupying the same footprint,thereby increasing the die area to be occupied by the drivers.

For comparison, assuming three metal layers 914 are employed at thelower levels, the architectures of FIGS. 2A and 3A may entail twointerconnect glue layers in a two deck memory array. FIG. 9B generallyillustrates these interconnect layers. The memory includes word lineslayers 916 and 920, bit line layer 918, glue layers 922 and 924 andthree additional layers of interconnect metal 914 (M1, M2 and M3) for atotal of five interconnect layers below the array. In contrast, thearchitecture of FIG. 4A can employ only one glue layer for either thetwo deck (FIG. 9C) or four deck (FIG. 9A) devices. This advantage ofreducing one interconnect glue layer is possible because of the centeredplacement of sockets within the driver groups. FIG. 9C generallyillustrates the interconnect layers for a two deck memory arrayoverlying drivers arranged according to the embodiment of FIG. 4A. Thememory includes word lines layers 916 and 920, bit line layer 918, aglue layer 924 and three layers of metal 914 (M1, M2 and M3), for atotal of only four interconnect layers below the array. The skilledartisan will appreciate that each level of metal can entail one or moredepositions and one or more lithographic steps, depending uponprocessing techniques employed.

Referring to FIG. 5, since the driver groups are distributed throughoutthe area of the active array (along with sockets), an efficient methodof connecting and driving these circuits is provided. The skilledartisan will appreciate, however, that the illustrated metallizationscheme has application to interconnections for integrated circuitsgenerally. FIG. 5 is an isometric illustration depicting a portion of anexample metallization scheme 500 with a plurality of metal levels. Ingeneral, metal levels in a semiconductor can be referred to numericallystarting at a metal level one (M1) and incremented with each additionalmetal layer. The embodiment of FIG. 5 includes four metal layers, M1,M2, M3 and M4, where M4 can also be referred to as a glue layer G1. Asnoted above, the term “glue layer” is employed herein to describe ametal layer that serves as an interface to form connections betweenlower metal layers (e.g., that interconnect driver circuits) and uppermetal layers (e.g., forming part of a memory array); however theprinciples and advantages of the metallization scheme 500 of FIG. 5 aremore generally applicable outside the environment of verticallyintegrated drivers and memory arrays, such that the more general term M4can be used in this description. As also noted above, M1 can serve as alocal interconnect for interfacing with semiconductor regions and forstrapping semiconductor diffusion regions, whereas M2 and M3 can serveas longer distance interconnects.

A plurality of conductive lines 530 are depicted as implemented in theM3 metal level. A plurality of conductive lines 520 are also depicted asimplemented in the M2 metal level. Further, a plurality of conductivelines 510 are depicted as implemented in the M1 metal level. A pluralityof conductive lines 540 are depicted as implemented in the M4 metallevel. In the illustrated embodiment, the conductive lines in each ofthe M1, M2, M3 and M4 metal layers are parallel with one another withineach level and cross with (e.g., are orthogonal with) conductors in theadjacent levels. This simplifies the design layout of each of theindividual metal layers. For example, photolithography optics can beoptimized more easily for parallel lines as compared to more complicatedpatterns, allowing for the smallest line widths and spacings for a givenlithography technique. Note, however, that the parallel line arrangementwithin one level can be limited to regions of the array, rather thanmaintained across the whole integrated circuit or across the wholearray, as will be better understood from the description of FIG. 6below. Furthermore, the parallel arrangement can be implemented by wayof predominantly parallel lines within a given region, wherein thepattern includes parallel lines in central portions of the region withsome deviations from parallel at the periphery of the region.

A plurality of electrically conductive vertical connectors are alsodepicted in FIG. 5. For example, a vertical connector 535 may provide anelectrically conductive connection between a conductive line in M3 and aconductive line in M4. Similarly, a vertical connector 525 may providean electrically conductive connection between an M2 line and an M3 line.A vertical connector 515 may also provide an electrically conductiveconnection between an M1 line and an M2 line. The vertical connectorsmay comprise one or more electrically conductive materials, such aspolysilicon, tungsten, and/or copper, for example.

In one embodiment, one or more of M4/G1 conductive lines 540 may connectwith a memory array (not shown) by way of one or more electricallyconductive vertical connectors (also not shown). Also, one or more of M1conductive lines 510 may connect with one or more drivers, such as wordline drivers and/or bit line drivers.

To route an electrical signal from one metal level to a differentlocation of a different metal level, relatively short lines, referred toas “paddles,” may be implemented in intermediate metal layers, asdepicted in FIG. 5. For example, to route a signal from an M1 line 510to an M3 line 530, an M2 paddle 522 may be utilized to route anelectrical signal between a connector 515 at one end of the paddle 522and a connector 525 at another end of the paddle, thereby providing aconductive path for routing an electrical signal from level M1 to levelM3. Each paddle 522/532 of M2/M3 is shorter than the conductive lines520/530 of those levels. For example, each paddle 522/532 may have alength between about 10 F and 128 F, if F represents the technology nodefor the integrated circuit, typically also representing the narrowestline width and spacing between lines for the integrated circuit. Incontrast, the conductive lines 520/530 of M2/M3 may have a lengthbetween about 200 F and several thousand times F, and may span theentire region (e.g., an electrode driver region). It will be understoodthat a paddle 522 in M2 permits the routing path for a signal tooverpass conductive lines 510 of M1, thus permitting those conductivelines 510 to pass straight through and area in which verticalconnections (with horizontal jogs) are made. Similarly, a paddle 532 inM3 permits the routing path for a signal to overpass conductive lines520 of M2, thus permitting those conductive lines 520 to pass straightthrough a region in which vertical connections (with horizontal jogs)are made.

Note that M2 paddle 522 runs substantially in parallel with a number ofother M2 lines 520. Note also that paddles run co-linear with otherpaddles in the same level, i.e., multiple short paddles extend along thesame linear “track.” Thus, each metal level is patterned predominantlywith parallel conductive lines, at least across a given region, and eachmetal level has parallel lines that are oriented non-parallel with(e.g., are orthogonal to) the parallel lines of vertically adjacentmetal levels. Thus within a region (e.g., a word line driver region or abit line driver region), each “track” or patterned line of a given metallevel is allocated to longer distance connections or to shorter paddles.Multiple tracks on each level can be allocated to paddles. This samestrategy can be employed in an orthogonal direction for the adjacentmetal levels above or below a given metal level. Accordingly, anefficient use of the available metallization is achieved within anygiven driver group.

A method of operating an integrated circuit can include routing a signalfrom a first semiconductor device to a second semiconductor device byway of a relatively short (e.g., between about 10 F and about 128 F)paddle. The signal can be routed through a paddle in an intermediatemetal level to a long distance line on another metal level, where thelong distance line is longer than the paddle. The first semiconductordevice can be a transistor at a substrate level, and the signal can berouted through the paddle on one level and the longer distance line onanother level to a second semiconductor device. As an example, CMOSdriver circuitry may call for an interconnect between an n-transistorand a p-transistor of the same driver region that are a relatively longdistance apart (e.g., between about 200 F and several thousand times F).Attempts to use M2 alone to form that connection would interfere withlonger conductive lines 520 of the same metal level and interfere withthe predominantly parallel arrangement in that region. In this example,both the first and second semiconductor devices can be transistors in anelectrode driver circuit. In another example, the first semiconductordevice can be a transistor at a substrate level and the secondsemiconductor device can be a memory cell (e.g., switch or storagedevice) in a memory array above the interconnect metal levels. As willbe better understood from the description of FIG. 6 below, the signalcan be repeatedly shunted between metal levels as the signal routecrosses boundaries, e.g., boundaries between driver regions of differenttypes.

Accordingly, FIG. 5 shows a single region of a semiconductor device.Within that region, each of at least two or at least three differentmetal levels (four shown) have predominantly parallel lines, some ofwhich (conductive lines) are longer and some of which are shorter(paddles). The parallel lines of each level cross with (e.g., areorthogonal to) the parallel lines of a vertically adjacent level, suchthat the line orientations alternate with each vertical level.

An application for the metallization scheme of FIG. 5 to an example ofdistributed driver architecture is described below and illustrated inFIG. 6. It will be understood, however, that the metallization scheme ofFIG. 5 has applications beyond the particular example of FIG. 6.

FIG. 6 is an illustration depicting a top view of a portion of anexample implementation of a memory device 600 comprising driver regions,such as bit line driver regions 610 and/or word line driver regions 620,arranged in a quilt pattern. The quilt architecture of FIG. 6 is similarto that of FIG. 4A, modified by expanding the word line driver regions620 to border with the bit line driver regions 610, and the word linedriver region are larger that the bit line driver regions due to greaterreal estate demands. Like FIGS. 3A and 4A, the column drivers,represented by bit line driver regions 612 in FIG. 6, are elongated inthe row or x-direction. Like FIG. 4A, a signal path traversing a path inan x- or y-direction passes over several row and column driver regionsalternately.

In the illustrated implementation, word line driver regions 620 and/orbit line driver regions 610 are broken up and redistributed, relative toperipheral driver arrangements such as FIGS. 2A-2B, in a manner suchthat a plurality of word line driver subsections are interspersed with aplurality of bit line driver subsections, for example. Also, in animplementation, socket regions 640 at which electrical connections maybe made to a memory array may be located at word line driver subsectionsand/or bit line driver subsections evenly or unevenly interspersedthroughout the quilt pattern. In the illustrated arrangement the socketregions 640 are each centered within the driver regions 610 and 620,minimizing distances from the socket regions 640 to the driver circuits.In an example implementation, connections from drivers in the regions610 and/or 620 to an overlying memory array may be made by way of one ormore metal levels formed between drivers in the regions 610 and/or 620and the memory array. This approach may also be used for driving signalsthat are common between drivers and therefore crosses multiple driverregion and tile boundaries.

The memory device 600 can include a metallization scheme with multiplemetal levels, such as M1, M2, M3 and M4. Within each driver region 610,620, the metallization can resemble FIG. 5, with predominantly parallellines at each level, and the lines of each level crossing with (e.g.,running perpendicular to) the lines of adjacent levels. However, becausethe desired orientations for lines of the lowest metal level M1 differbetween word line driver regions 620 and bit line driver regions 610,the entire metallization stack can be rotated 90° at boundaries betweendifferent regions 610 and 620. Thus, M1 lines in a bit line driverregion 610 are orthogonal to M1 lines in an adjacent word line driverregion 620; M2 lines in a bit line driver region 610 are orthogonal toM2 lines in an adjacent word line driver region 620; etc.

In some implementations, a memory device may comprise a semiconductorlevel, such as silicon, including one or more word line driver regions620, and/or one or more bit line driver regions 610. A memory device mayfurther comprise one or more first signal paths 611, positionedsubstantially along a first direction. As shown, the first signal path611 crosses over multiple alternating different driver regions 610 and620. Because any given metal level has orthogonal lines from bit lineregion 610 to word line region 620, the one or more first signal pathssubstantially alternate between a first metal level, such as M2 602, anda second metal level, such as M3 603, positioned above a semiconductorlevel at least in part in accordance with the arrangement of drivers. Anexample implementation of a memory device may also comprise one or moresecond signal paths 621, oriented to cross with (e.g., orthogonal to)the first direction, wherein one or more second signal paths mayalternate between metal levels, such as a M3 603 and M2 602, as theycross over correspondingly different circuit regions, such as thedistributed word line driver regions 620 and bit line driver regions 610of the illustrated embodiment. In the illustrated embodiment, the firstsignal paths 611 (extending in the y direction) are defined in metallevel M2 over word line driver regions 610, but are defined in metallevel M3 over bit line driver regions 620. In contrast, the secondsignal paths 621 (extending in the x direction) are defined in metallevel M3 over word line driver regions 610, but are defined in metallevel M2 over bit line driver regions 620. Accordingly, the first andsecond signal paths 611 and 621 do not interfere with each other wherethey cross over, nor do they interfere with other conductive linesdefined in M2 and M3 for the interconnecting the distributed drivercircuitry.

Accordingly, a signal path can alternate between metal levels tocontinue to travel in one direction (e.g., x-direction or y-direction)while crossing boundaries at which there is a switch in the orientationsof parallel lines in a single metal level. Shunting of the signal paths611 and 621 between metal levels can be facilitated by short metallines, such as the paddles 522 or 532 of FIG. 5, without deviation fromthe parallel line arrangement for any given metal level within a givenelectrode driver region 610 or 620.

As noted, the metal level that interfaces with the semiconductor devicesin the driver regions (e.g., M1) can have a parallel line or “routingtrack” orientation chosen to enable efficient connection for a word linedriver group within a word line driver region 620. However, thedirection of the routing tracks may be changed for that metal levelgrouping bit line driver regions 610, in which M1 interconnect to thebit line drivers may be orthogonal to the M1 interconnects to the wordline drivers. In this way, a metallization structure will changedirection at boundaries of driver regions that interconnect tosemiconductor devices and drive in orthogonal directions. Thus to enablea signal to travel across multiple driver regions, in the x-direction,the same electrical signal will transition from one metal level toanother as it crosses different driver regions. In a similar manner, asignal that travels in the y-direction will transition metal levels asit crosses the different driver regions. This organization of routingtracks, paddles and orthogonal conductors as described herein enablesefficient use of the metal levels. The metallization scheme describedherein is particularly, but not exclusively, useful for the distributeddriver memory architectures of FIGS. 3A-4B and 6.

FIG. 7A is an isometric illustration depicting three metal levels. Inparticular, an interface between a lower interconnect metal level and ahigher memory array metal levels is illustrated. The lower interconnectmetal level of the illustrated embodiment includes conductive lines 710of the glue layer M4/G1 of FIG. 5 and the higher memory array metallevels include memory array electrode lines. In the illustratedembodiment, the electrode lines are represented by two levels of rowelectrodes in the form of word lines 720 and 722. The memory storageelements and bit lines are not shown for clarity, but it will beunderstood that similar socket regions can be employed for connectinginterconnects to central points along column electrodes, or bit lines,rather than near the ends of such memory electrode lines. The memory maycomprise a PCM cross-point memory array, although claimed subject matteris not limited in this respect.

Socket interconnect region 700 is a region of the memory device wherevertical connections are made between the memory array electrodes andlower levels. The socket interconnect region 700 may comprise the socketfor a two-deck memory array, comprising, for example, a first pluralityof word line electrodes 720 and a second plurality of word lineelectrodes 722. In operation electrical signals may be communicatedbetween the word lines and a plurality of word line drivers through theplurality of interconnect metal levels, including glue level G1. Some G1conductive lines 710 electrically connect with word line electrodes 720of the lower deck through vertical connectors 760 and other G1conductive lines 710 connect to word line electrodes 722 of the upperdeck by way of vertical connectors 740. Note that, despite theappearance of FIGS. 3A, 4A and 6, the location of the socketinterconnect region 700 need not vertically align with the location ofthe interconnect socket (e.g., 640 in FIG. 6) for the drivers that areconnected to the illustrated word lines 720 and 722. The connectionpoint to the electrode lines can be laterally shifted with respect tothe connection point to the driver regions, as they are connected by wayof multiple interconnect levels (e.g., M1-M4).

It is noted that the vertical connectors between electrodes 710 of theglue level G1 and word line 722 can be routed through a gap 721 that isformed in neighboring word lines 720 in the same level. As explainedabove with reference to FIG. 4A, the staggered pattern of the word lineelectrodes, or group of electrodes, can create gaps 721 between the endsof word lines that correspond to the center location of adjacent wordlines, as illustrated in FIG. 7A. In particular, a gap 721 is formed inthe region between ends of two terminated word line electrodes 726 and728 and ends of terminated word line electrodes 726′ and 728′ on theother side of the gap 721, which creates room for vertical connectors760 to adjacent word line electrodes 724 and 730 on the same metallevel, as well as for vertical connectors 740 to word line electrodes722 of a higher metal level or higher ‘memory deck.’ The terminatedwords lines 726, 726′ and 728, 728′ are aligned in the illustratedembodiment. These gaps 721, as shown in FIG. 7A, provide a path to routethe vertical connectors 740 and 760.

FIG. 7B illustrates a top view of word lines 720 of FIG. 7A and verticalconnectors 740 and 760. In an implementation, inter-level verticalconnectors 760 may extend from central points along word lines 724 and730 to other vertical levels, such as points along one or moreconductive lines 710 in the glue level G1 (FIG. 7A). While shown asconnecting to the sides of word lines 724 and 730, it will be understoodthat the vertical connectors 760 can instead connect to the bottomsurfaces of the words lines 724 and 730. As previously noted, in someimplementations, the connection points between the vertical connectors760 and the word lines 724 and 730 is closer to mid-points along theword lines 724 and 730 than to either end point of the word lines 724and 730. In some implementations, the connection point are positioned adistance of at least about 40% of the length of the word line fromeither end of the word line, such that the connection point is withinthe middle 20% of the length of the line. The sockets and centralconnections can be similar for sockets for the bit lines (not shown)

Also, vertical connectors 740 may extend from lower levels, such aspoints along one or more conductive lines 710 in the glue level G1 (FIG.7A) to one or more upper deck word lines 722 (FIG. 7A). Gaps 721 may belocated in spaces between word lines, such as lower-deck word lines 726and 728 and aligned word line 726′ and 728′. The number of terminatinglines may change to enable more or less room to allow vias to passthrough as required by the process. As will be better understood fromthe description below of FIG. 8B, sockets can alternatively be createdin regions between ends of terminated lines, but the lines terminated atthe sockets need not be aligned with one another

FIGS. 7A and 7B illustrate the concept of connections to the arraywithout regard for the individual processing steps or layers for formingthose connections. The concept is general in that it can be extended orsimplified to support the requirements for word line sockets, bit linesockets and sockets for support of multiple decks of a 3D memory array.The illustration depicts a socket that may be built with direct printtechnology, where a masking process defines the actual line or space ofthe word line or bit line electrode. The quilt socket, defined in gapsbetween terminations or ends of electrode lines, allows electricalconnectors (e.g., vertical connectors 760) to terminate at the socket,and space is available within the socket to connect to electrode linesthat do not terminate at the socket (pass adjacent or through the socketregion) by means of a contact via or other connection. Additionally,some electrical connectors (e.g., vertical connectors 740) can passthrough electrically unimpeded through the socket, e.g., to connect withelectrode lines at a different vertical level, such as for a multideckor multilevel memory array.

With reference to FIGS. 8A and 8B, these criteria can also be met in thecontext of self-aligned double patterning (SAPD), which is a techniquefor pitch-multiplication. FIG. 8A shows an example of a pattern ofsacrificial mandrels 800 that can be defined by a masking process, suchas photolithography. The mandrels 800 can be directly formed bylithography or can be formed by a masking process that transfers thepattern from upper resist patters to lower hard mask material(s). In theillustrated embodiment, the sacrificial mandrels 800 include elongatedpass-through mandrel lines 805, terminated mandrel lines 806, transversemandrel jogs 810 and isolated mandrel features 815. In this case,including the transverse mandrel jogs 810 along the patternedpass-through mandrel lines 805 facilitates line spacing for properplacement of the isolated mandrel features 815, which in turn can beused to pattern vias for vertical connections. The terminated mandrellines 806 are not aligned but facilitate creation of room for theconnections being made in the socket.

FIG. 8B shows a pattern of spacers that can be obtained by formingsidewall spacers over mask or hard mask features having the pattern ofthe sacrificial mandrels 800 of FIG. 8A, and that spacer pattern, or thenegative image of it, can also represent a pattern of memory electrodelines 850 patterned by use of the spacers as a hard mask. Spacers can beformed by a conformal thin film deposition over the mandrels 800,followed by anisotropic etch to remove horizontal portions of the filmand leave the spacers on the vertical sidewalls of the mandrels 800,after which the mandrels 800 can be removed by selective etching. Thesespacers can then be used to pattern metal lines to form the illustratedpattern of memory electrode lines 850.

The memory electrode lines 850 include pass-through electrode lines 855,which include electrode jog segments 860 that extend transverse to thedirection of electrode elongation, and terminated electrode lines 856.The pass-through electrode lines 855 of the illustrated embodiment areadjacent to the terminated electrode lines 856, like the embodiment ofFIGS. 7A-7B, and pass through the interconnect socket region. In thecase of FIG. 8B, the interconnect socket region is formed in a gapbetween ends of terminated electrode lines 856 that do not align. Theelectrode lines 855 and 856 have double the density of the mandrelslines 805 and 806 because two spacer lines forming these electrode lines855 or 856 are formed on opposite sidewalls of each mandrel line 805 or806. It will be understood that two spacer lines as formed also connectto one another as formed by looping around the end of a mandrel line 805or 806. However, an additional chopping mask can be employed to cut offthe spacer loop ends and prevent shorting of the eventual conductivelines. For example, boxes 857 can represent openings in a chopping maskthrough which etchant can cut off the spacer loop ends. Alternatively,boxes 857 can represent a blocking mask that covers the loop ends andserves to prevent transfer of spacer loop end parts of the spacerpattern when transferring the spacer pattern to a lower level, e.g., toanother hard mask level or into an interlevel dielectric when conductingdamascene patterning. Similar boxes 859 can represent chopping orblocking mask features that provide two isolated spacer features thatcan used to define two vertical connectors 865 for every one isolatedmandrel feature 815.

In different embodiments, each of the memory electrode lines 855 and 856can represent a row electrode (e.g., word line) or a column electrode(e.g., digit or bit lines), defined by spacers formed over the mandrelpattern 800 of FIG. 8A (e.g., using the spacers as a hard mask topattern a blanket metallic layer, or to pattern an insulator for adamascene process). Each isolated spacer feature can represent thelocation of a pass-through vertical connector 865. In FIG. 8B, thepass-through vertical connectors 865 do not contact the electrode lines855 and 856 of the illustrated electrode level. Rather, the pass-throughvertical connectors 865 can connect lower levels (e.g., G1 glueelectrodes, ultimately electrically connected to electrode drivers) toupper levels (e.g., electrodes of a memory array upper deck), and simplypass through the level of the electrodes represented by the electrodelines 855 and 856. The vertical connectors 865 can connect withelectrode line of the memory array in the upper levels at centrallocations along the electrode lines, as described above.

Thus FIGS. 7A-8B demonstrate the concept of socket interconnect regionsfor vertical connectors to electrodes, such as connections from lowerlevel drivers to memory electrode levels and/or through an interveninglevel of electrodes to upper level electrodes. The socket interconnectregions can be employed solely for vertically connectors to theelectrodes at the electrode level of the socket region; solely forpass-through vertical connectors without electrically contacting theintervening level of electrodes (see isolated spacer features in FIG.8B); or for both pass-through connectors and connectors that terminateat the intervening level (see vertical connectors 740 and 760 in FIGS.7A-7B). Connections can be made at central locations of electrode lines.Accordingly, connections for driving electrodes can be made in the midstof an array of electrode lines for a memory array, rather than beinglimited to peripheral locations, and average or maximum lateraldistances from each driver to its associated memory cells can beminimized. The socket interconnect regions can be defined by gapsbetween terminations or ends of electrode lines that are aligned (FIG.7B) or by gaps defined between terminations or ends of electrode linesthat are not aligned (FIG. 8B). For example, none of the terminatedspacer lines 856 of FIG. 8B are aligned, but it can be seen how theynevertheless define a gap along the direction of elongation in theregion between the terminations. Vertical connectors can be made inthose gaps to electrode lines that are adjacent or bordering on gap(FIG. 7B) and/or to adjacent electrode lines that run through the gaps(FIG. 8B). For example, in FIG. 8B vertical connectors (not shown) canconnect to the underside of the transverse electrode jog segments 860within the socket interconnect region.

While the pitch multiplication technique of FIGS. 8A-8B has beendescribed in terms of spacers on sacrificial mandrels, the skilledartisan will appreciate that pitch multiplication can be achieved usingother techniques. For example, and without limitations, the spacerprocess can be conducted twice to achieve four times the density and onequarter line width as compared to lithography-defined features;non-spacer processes can be performed, such as repeating a lithographicprocess twice with a lateral shift between masks; etc.

For the distributed driver and staggered electrode arrangements of FIGS.3A, 4A and 6, it will be noted that a distinct memory cell address tiledoes not necessarily correspond to the physical boundaries of thesub-array tiles. The distributed nature of the drivers and sockets andthe overlapping nature of the electrodes means that there is no longer anatural correlation between driver group location and location of acorresponding driven memory cell array. Thus a memory cell addressdecoding strategy should take into account the overlap in order to avoidunintended selection of bits in the array. If a word line is 1k bits inextent and a bit line is 1k bits in extent, then the tile is the groupof drivers needed to uniquely drive 1K×1K bits. In the illustrateddistributed arrangements, this group of drivers is generally locatedover a footprint that is different from the physical location of thebits which it addresses. In other words, even though a memory array canoverlie and thus share real estate with its word line drivers and bitline drivers, the locations of the drivers need not correspond to thelocations of the memory cells that they address.

Accordingly, a collection of such tiles can drive array word lineelectrodes and bit line electrodes that extend beyond the boundary ofthese tiles. Similarly, any collection of these tiles can have word lineand bit line electrodes that extend into the regions occupied by thesetiles from outside the boundary of those regions. For example, withreference to FIG. 4A, the word line driver regions 410 in the lower leftcorner of the array is shown driving a word line 430 that extends to theright to terminate above a different word line driver region 410.Moreover, that centrally connected word line 430 is also shown extendingto the left, which may be outside the footprint of the memory array andthus partially orphaned from memory cells. Conversely, the staggeredarrangement will generally result in memory cells that are orphaned fromword line or bit line drivers. The flexible nature of the metallizationscheme enables matching of orphaned drivers in one part of the arraywith orphaned memory cells in another part of the array.

Accordingly, because locations of memory cells need not correspond tolocations of the driver circuitry that addresses those cells. Thestaggered arrangement of the row and column electrode lines particularlyleads to dangling electrode lines at the periphery of the array.However, because the orphaned cells and drivers on one end of the arraycan be matched with the orphaned cells and drivers on the opposite edgeof the array, the resultant connections electrically behave as ifelectrode lines on one edge of the array wrap around a cylindrical shapeto address memory cells on the opposite edge of the array. The extensionof electrode lines to connect with memory cells above adjacent tilesrepresents meshing of adjacent tiles, and peripheral tiles can mesh withtiles on opposite sides of the array to make a continuous mesh. Becausethis logical “wrap” effect applies in both dimensions of row electrodesand column electrodes, the array of memory cells and the electrodes thataddress them can be logically represented on the surface of a torus 1000as illustrated in FIG. 10 showing a group of word lines 1010 and a groupof bit lines 1020. Word line group 1010 represents a collection of wordline segments or groups of segments that may be staggered from eachother, such as the illustrated group of four word lines 430 shown inFIG. 4A that gets repeated for adjacent tiles. Similarly bit line group1020 represents a collection of bit line segments or groups of segments,such as the illustrated group of four bit lines 432 shown in FIG. 4Athat gets repeated for adjacent tiles. Electrodes that extend outsidethe tiles on the upper boundary of the collection of tiles, matches theelectrodes that extend into the bottom boundary of the tiles. Similarly,electrodes that extend into the left boundary of a tile match theelectrodes that extend into the right boundary of that tile. To achievemapping of this logical toroidal surface onto the planar surface of asilicon wafer, some duplication of decoding circuits may be entailed.Any such decoding overhead can be amortized over a collection ofcontiguous tiles or patches.

CONCLUSION

Embodiments herein provide for row and column drivers, optionally alongwith other logic circuitry for memory management, in row and columndriver regions within a shared footprint of a memory array, e.g., belowthe memory array. Disjointed driver regions can be distributed acrossthe footprint, and connections from drivers to the row and columnelectrode lines (e.g., word and digit lines) can also be distributedacross the footprint. The distribution can resemble and patchwork orquilt pattern. Bringing logic circuitry within the footprint of thememory array can save footprint and circuit complexity both by reducingreal estate traditionally occupied by “peripheral” circuitry and byshortening the distance from the logic circuitry to the memory cells,thus relaxing specifications for the logic circuitry. Because the realestate needs of logic circuitry can exceed those of the memory arrayserved by it, particularly (but not exclusively) for multi-deck memoryarrays, the arrays need not be scaled to be smaller in size than theunderlying logic circuits. Accordingly, further savings can be obtainedby scaling the memory array only as much as needed to cover thedistributed logic circuitry below. The critical dimensions of the memoryarray can thus also be more relaxed, and less expensive patterningprocesses can be employed compared to cutting edge technology.

Metallization schemes described herein can facilitate connecting thedistributed logic circuits to overlying memory array(s); however, themetallization scheme can also be employed independently of the logiccircuit placement, and independently of interconnect socket designsdescribed herein. The metallization schemes can include maintainingparallel lines within a particular region at a particular metal level,and maintaining parallel lines that cross (e.g., perpendicularly) withthose lines in adjacent metal levels. Such a parallel arrangements ateach level are efficient from a lithography point of view. The crossingorientations can alternate from level to level within the region. Theparallel lines can include both long distance lines and comparativelyshorter paddles, where multiple paddles can be co-linear along sametrack. As an example, paddle length can be 10 F and 128 F, where Frepresents the narrowest line width in the integrated circuit, whereaslong distance line can have a length from about 200 F to thousands timesF. In operation, such paddles can be used to route signals between lowerand higher levels, shifting the signal path by a relatively shortdistance to a longer crossing line longer in another interconnect level.Signals can thus be shunted in various directions without deviating fromthe parallel arrangement within a region on a metal level.

Interconnect socket designs described herein can facilitate connectingthe distributed logic circuits to overlying memory array(s); however,the interconnect sockets can also be employed independently of logiccircuit placement, and independently of metallization schemes withalternating parallel lines. Interconnect socket regions can be formed ingaps between the ends of terminated memory electrode lines in the samelevel (e.g., row or column electrode lines), and vertical connectorsmake contact with non-terminated lines that pass through or by thesocket interconnect regions. Memory electrodes can be staggered ineither or both row and column directions, and connections to electrodelines in the interconnect socket regions can be made at central pointsalong the lengths of the electrode lines. Among other benefits, drivingmemory electrodes from central points and staggering the lines ensuresthat an addressed cell cannot be both farthest away from its columndriver and farthest away from its row driver.

Systems including the memory devices described herein can additionallyinclude one or more processors in communication with the logic circuitryof the memory devices. Such systems can additionally include componentsto define electronic devices, such as, but not limited to, computers,mobile phones, electronic games, cameras, music players, etc.

The terms, “and”, “or”, and “and/or” as used herein may include avariety of meanings that also are expected to depend at least in partupon the context in which such terms are used. Typically, “or” if usedto associate a list, such as A, B or C, is intended to encompass A, B,and C, here used in the inclusive sense, as well as A, B or C, here usedin the exclusive sense. In addition, the term “one or more” as usedherein may be used to describe any feature, structure, or characteristicin the singular or may be used to describe a plurality or some othercombination of features, structures or characteristics. Though, itshould be noted that this is merely an illustrative example and claimedsubject matter is not limited to this example.

In the preceding detailed description, numerous specific details havebeen set forth to provide a thorough understanding of claimed subjectmatter. However, it will be understood by those skilled in the art thatclaimed subject matter may be practiced without these specific details.In other instances, methods or apparatuses that would be known by one ofordinary skill have not been described in detail so as not to obscureclaimed subject matter.

While there has been illustrated and described what are presentlyconsidered to be example features, it will be understood by thoseskilled in the art that various other modifications may be made, andequivalents may be substituted, without departing from claimed subjectmatter. Additionally, many modifications may be made to adapt aparticular situation to the teachings of claimed subject matter withoutdeparting from the central concept described herein.

Therefore, it is intended that claimed subject matter not be limited tothe particular examples disclosed, but that such claimed subject mattermay also include all aspects falling within the scope of appendedclaims, and equivalents thereof.

1. A method, comprising: forming a plurality of row drivers and aplurality of column drivers below and within a footprint of an array ofmemory cells.
 2. The method of claim 1, wherein forming the row driversand column drivers comprises partitioning the row drivers into aplurality of subsets of row drivers and partitioning the column driversinto a plurality of subsets of column drivers and interspersing thesubsets of row drivers among the subsets of column drivers.
 3. Themethod of claim 2, wherein forming the row drivers and column driverscomprises forming word line drivers and bit line drivers.
 4. The methodof claim 2, wherein forming the row drivers and column drivers comprisesdistributing the row drivers and column drivers across the footprint ofthe memory array in disjointed row driver regions and disjointed columndriver regions, such that row electrodes connecting the row drivers tomemory cells of the memory array are staggered, and column electrodesconnecting the column drivers to the memory cells of the memory arrayare staggered.
 5. The method of claim 4, wherein distributing the rowdrivers and column drivers comprises grouping row drivers into the rowdriver regions and grouping column drivers into the column driverregions such that the row electrodes and the column electrodes arestaggered in bundles.
 6. The method of claim 4, wherein furthercomprising connecting each row electrode to a central part of one of therow driver regions and connecting each column electrode to a centralpart of one of the column driver regions.
 7. The method of claim 4,wherein distributing row drivers and column drivers comprises forming arepeating quilt-like pattern of the row driver regions and column driverregions.
 8. The method of claim 7, wherein forming the repeating patterncomprises forming row driver regions such that they border on columndriver regions.
 9. The method of claim 1, further comprising: formingone or more interconnect levels over a circuit level, the circuit levelcomprising the row drivers and the column drivers; and forming the arrayof memory cells over the one or more interconnect levels.
 10. The methodof claim 9, wherein the forming the array of memory cells over the oneor more interconnect levels comprises forming an array of phase changememory cells between row electrodes and column electrodes in across-point memory array.
 11. The method of claim 9, wherein forming thearray of memory cells over the one or more interconnect levels comprisesscaling the array to cover logic circuitry in the circuit level for thearray.
 12. A memory device, comprising: an array of memory cells; and aplurality of row drivers and a plurality of column drivers distributedwithin a footprint of the array of memory cells, the row drivers andcolumn drivers being distributed across the footprint in a plurality ofdisjointed row driver regions and disjointed column driver regions. 13.The memory device of claim 12, wherein the row driver regions and columndriver regions are arranged in a repeating pattern of tiles across thefootprint.
 14. The memory device of claim 13, wherein the repeatingpattern includes alternating row driver regions within column driverregions in both row and column directions.
 15. The memory device ofclaim 13, wherein each tile comprises at least a portion of one of therow driver regions and at least a portion of one of the column driverregions.
 16. The memory device of claim 12, wherein the array of memorycells comprises an array of phase change memory cells.
 17. The memorydevice of claim 12, wherein the array phase change memory cellscomprises a multi-deck array of phase change memory cells.
 18. Thememory device of claim 12, further comprising staggered row electrodesconnecting the row drivers to the memory cells of the array, andstaggered column electrodes connecting the column drivers to the memorycells of the array.
 19. The memory device of claim 18, the rowelectrodes and the column electrodes are staggered in bundles.
 20. Thememory device of claim 12, wherein each row electrode connects to aportion of one of the row driver regions centered along the rowdirection, and each column electrode connects to a portion of one of thecolumn driver regions centered along the column direction.
 21. Thememory device of claim 12, wherein the row driver regions and the columndriver regions are distributed to alternate along a first direction;further comprising a first interconnect signal path oriented along thefirst direction, the first interconnect signal path alternating betweena first metal level and a second metal level positioned above the rowdrivers and the column drivers as the first interconnect signal pathcrosses boundaries between the row driver regions and the column driverregions.
 22. The memory device of claim 21, further comprising a secondinterconnect signal path positioned and oriented to cross with the firstinterconnect signal path, the second interconnect signal pathalternating between the second metal level and the first metal level asthe second interconnect signal path crosses boundaries between the rowdriver regions and the column driver regions.
 23. The memory device ofclaim 22, the first interconnect signal path and the second interconnectsignal path occupy opposing levels of the first and second metal levelsat locations where the first interconnect signal path intersects thesecond interconnect signal path.
 24. The memory device of claim 12,wherein the row drivers comprise word line drivers connected to wordline electrodes of the array of memory cells, and the column driverscomprise bit line drivers connected to bit lines of the array of memorycells.
 25. The memory device of claim 12, further comprising additionalcircuitry for operating the array of memory cells within the footprint.26. A system, comprising: a memory device comprising an array of memorycells occupying a footprint; and a plurality of word line drivers anddigit line drivers in a circuit level positioned below the array ofmemory cells, wherein the circuit level comprises a plurality of wordline driver connection points and digit line connection pointssubstantially distributed across the footprint.
 27. The system of claim26, wherein the memory device further comprises interconnects formed inmetal levels positioned between the circuit level and the array ofmemory cells, the interconnects electrically coupling the word linedriver connection points and the digit line driver connection points tothe array of memory cells.
 28. The system of claim 26, wherein the arrayof memory cells comprises word lines positioned substantially along afirst direction and digit lines positioned substantially along adirection substantially orthogonal to the first direction.
 29. Thesystem of claim 28, wherein individual memory cells of the array ofmemory cells are located at intersections of the word lines and digitlines.
 30. The system of claim 28, wherein the word lines are staggeredalong a word line direction, and the digit lines are staggered along adigit line direction.
 31. The system of claim 26, wherein the word linedrivers are each formed within one of a plurality of disjointed wordline driver regions distributed across the footprint, and the digit linedrivers are each formed within one of a plurality of disjointed digitline drivers distributed across the footprint.
 32. The system of claim31, wherein each the word line connection points is centered along aword line direction within one of the word line driver regions, and eachof the digit line connection points is centered along a digit linedirection within one of the digit line driver regions.